1. Field of the Invention
The present invention relates to interworking between a macro Access Services Network (ASN) and a femto ASN in a mobile network. More particularly, the present invention relates to a method and a system for successfully paging a Mobile Station (MS), when the MS located in an area where a macro ASN and a femto ASN are linked is in an idle mode.
2. Description of the Related Art
For a Mobile Station (MS) registered in a Mobile Worldwide Interoperability for Microwave Access (M-WiMAX) network and receiving a service in an active state, if there is no more data to transmit and/or receive, the MS transitions to an idle mode to save its power, thus preventing power consumption. After the MS transitions to the idle mode, if there is traffic to be transmitted to the MS, an Access Services Network Gateway (ASN-GW) awakes the MS by sending a paging message to a Base Station (BS) corresponding to a paging group of the MS and then performs a network re-entry process.
Even an M-WiMAX femto BS may awaken an MS in an idle state by sending a paging message through the above procedure.
FIG. 1 illustrates a Network Reference Model (NRM) according to the related art.
Referring to FIG. 1, an NRM includes a macro ASN including a macro BS and a macro ASN-GW; a femto ASN including a WiMAX femto cell Access Point (WFAP), a Security Gateway (SeGW), a femto-GW, and a Self Organization Network (SON); a Connectivity Service Network (CSN) (or Network Service Providers (NSP)) including an Authentication, Authorization, and Accounting (AAA) and a Home Agent (HA); and a femto NSP including a WFAP AAA, a WFAP Management (WFAP Mgmt), a bootstrap server, interwork with one another through interfaces such as R1, R4 and R6.
FIG. 2 illustrates a configuration of a macro ASN and a femto ASN according to the related art.
Referring to FIG. 2, a macro ASN 220 and a femto ASN 210 are configured independently. As to a femto ASN forming a femto cell, the femto ASN may be configured in a macro ASN, or the femto ASN may be configured near a macro ASN. Because the femto ASN is a micro network formed for the use of home, personal, office, etc., numerous femto BSs may exist (e.g., hundreds of thousands of femto BSs), and a user may freely control an on/off state of the femto BSs at his or her discretion.
Therefore, since it is not possible to estimate which femto BSs exist near a macro BS, it is almost impossible to pre-configure neighboring information and paging information of femto BSs in a macro ASN.
For example, since the femto ASN is a micro home BS, an MS 200 registered in a femto BS #2 208 in FIG. 2 is not registered in other femto BSs (i.e., a femto BS #1 or a femto BS #3 in FIG. 2). That is, as to a paging area of an MS registered in one femto BS, only a femto BS in which the MS is registered and a macro BS is linked thereto are valid as the paging area. Further description in relation to FIG. 2 will be provided below.
Even though a femto BS is for home use and signals transmitted and received to/from the femto BS are only valid in a building, considering that an MS may be located in the boundary of the building or in macro coverage outside the building, it is apparent that sending a paging message not only in a femto area but also in a macro area is superior in performance improvement to sending a paging message only to the registered femto BS.
Assume that an MS transitions to an idle mode after performing a handover from a macro ASN to a femto ASN. If there is traffic in the network to be delivered to the MS, a BS of a femto ASN to which the MS belongs to orders the MS to transition to an active state through a network re-entry process by sending a paging message.
Even though an MS has performed an idle handover from a femto ASN to a macro ASN, if the MS has not yet performed Location Update (LU) for the reason that it has not yet detected the change in its Paging Group (PG), a paging message cannot be sent from the macro ASN to the MS, but is sent from the femto ASN to the MS, failing to awaken the MS.
On the contrary, even when an MS has moved to a femto ASN in an idle state after performing a handover from the femto ASN to a macro ASN, the MS may fail to be awakened.
Therefore, a need exists for a method and a system for improving a paging success rate of an MS that has transitioned to an idle state after performing a Hand-in handover from a macro ASN to a femto ASN or performing a Hand-out handover from a femto ASN to a macro ASN.